06-18-2009 06:08 AM - edited 03-06-2019 06:20 AM
---------- ---------- ----------
| SW 1 |---trunk---| SW 2 |---trunk---| SW 3 |--------- rest of VTP domain
---------- ---------- ----------
| |
client 1 client 2
(I hope the little schema is readable, because in the post form it wasn't. If not I'm gonna send another one in jpg)
Hi, this is a question about a strange observation. Has someone already see this, or is it something normal and explanable ?
The situation is : all 3 swithes are in the same VTP domain (dom1), in client mode, in version 1, without password.
Everything's OK. The goal is to move SW1 and SW 2 in transparent mode in order to create a local VLAN that is useless in the
rest of the VTP domain.
The problem is : when I configure SW 1 in transparent mode, SW 1 becomes isolated, he's not able to join the rest of the
network, and the client 1 neither. In this state, everything is ok on SW 2. When then I configure SW 2 in transparent mode
too, SW 1 retreive its connectivity and client 1 too, and the situation is globally OK.
The question is : why is there a connectivity problem when only SW 1 is in transparent mode ??? I may have understood if the
domain were not the same, but it is not the case.
I hope this question is not so stupid.
Regards
Thomas
06-18-2009 06:14 AM
06-18-2009 10:27 AM
Can you send "sh vtp status" from both switches?
Thanks,
Mohamad
06-19-2009 01:26 AM
show vtp status for SW1 before modification
WS-2950-LVD-3#sh vtp status
VTP Version : 2
Configuration Revision : 73
Maximum VLANs supported locally : 250
Number of existing VLANs : 43
VTP Operating Mode : Client
VTP Domain Name : dom1
VTP Pruning Mode : Enabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0xB8 0x3C 0x72 0x69 0xAC 0x11 0x61 0x37
Configuration last modified by xxx
For SW2 :
WS-3560-LVD-2#sh vtp status
VTP Version : running VTP1 (VTP2 capable)
Configuration Revision : 73
Maximum VLANs supported locally : 1005
Number of existing VLANs : 43
VTP Operating Mode : Client
VTP Domain Name : dom1
VTP Pruning Mode : Enabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0xB8 0x3C 0x72 0x69 0xAC 0x11 0x61 0x37
Configuration last modified by xxx
For SW3 :
SW-C2960-30T1-020#sh vtp status
VTP Version : 2
Configuration Revision : 73
Maximum VLANs supported locally : 255
Number of existing VLANs : 43
VTP Operating Mode : Client
VTP Domain Name : dom1
VTP Pruning Mode : Enabled
VTP V2 Mode : Disabled
VTP Traps Generation : Enabled
MD5 digest : 0xCF 0xBC 0xD1 0x09 0xDB 0x14 0x3C 0xE3
Configuration last modified by xxx
06-18-2009 11:59 PM
what do you mean with:
cannot join the rest of the network?
connectivity issues?
If yes, make sure that the VLANS you create on sw1, are known on the other switches and allowed over the trunk
06-19-2009 01:21 AM
Thank you for your answer.
Yes, when i said "cannot join te rest of the network" I meant "connectity issue".
Of course the vlans known on the 3 switches are the same, because they were all in client mode before the modification, and were synchronized. When you switch in transparent mode, the vlan database in not reseted, just the revision number.
The vlan for which there is connectivity issue are allowed on the trunks.
06-19-2009 02:01 AM
Hi,
I see you have pruning enabled. This might be an issue when changing to transparent mode. Take a look at the following thread:
http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=LAN%2C%20Switching%20and%20Routing&topicID=.ee71a04&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40^1%40%40.2cd35857/3#selected_message
06-19-2009 02:09 AM
Thomas,
Please post a "show interface trunk" command on Sw1 and Sw2.
Toshi
06-19-2009 06:12 AM
Thank you for the answer.
I had already thought about this, it is a good idea, but I would have understood if I moved first the SW 2 int transparent which would have cut the domain between SW1 and SW3 (although the domain is the same on all switches and so vtp v1 should let the vtp packets pass). But I first moved SW1. Besides, the issue should be the same on SW2 in this case, but it is not.
I took a look at the command "show int trunk" but the Vlan for which there is the issue is not pruned, wherever ! That's why I don't understand.
06-22-2009 02:13 PM
Everything you wanted to know about VTP:
http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml
There is a flash animation that goes along with the above doc, which is here: http://www.cisco.com/warp/public/473/vtp_flash/
I didn't see a VTP server on your three switches.
06-23-2009 04:58 AM
In fact I think the thread you indicated is very interesting !
Thanks to paul malysz too, I took a look to the troubleshooting part of the VTP guide and I conclude that VTP pruning and mode transparent are not good friends at all... even if the domain is correct.
Regards
Thomas
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